The present invention relates to valves for vacuum die casting machines. More particularly, the present invention relates to a valve having a slotted member that is movable between a fluid-passing position and a fluid-blocking position.
A cast part produced from a die under a vacuum has less porosity and a superior hardware finish compared with similar parts cast under ambient air pressure conditions. Die casting machines for feeding and casting under vacuum incorporate a hermetically sealed part cavity defined by a pair of dies fluidly associated with a vacuum pump. In such machines a vacuum is first created within the cavity. Molten metal enters the cavity, being moved partially because of the vacuum and partially because of the movement of a shot plunger driven by a power cylinder.
Between the mold cavity and the vacuum pump is a vacuum valve that is controlled to selectively interrupt fluid communication between the cavity and the pump at a preselected interval during the casting process. The vacuum valve can only remain open to allow the desired vacuum to be created within the cavity but must be closed prior to the passage of molten metal.
Several types of systems and valves exist which are directed to the evacuation of fluid from a die cavity. The systems and valves are illustrated by the following U.S. patents: F. Hodler, U.S. Pat. Nos. 2,785,448, Mar. 19, 1957; F. Hodler, U.S. Pat. No. 2,867,869, Jan. 13, 1959; D. M. Morgenstern, U.S. Pat. No. 2,904,861, Sep. 22, 1959; W. Venus, U.S. Pat. No. 3,070,857, Jan. 1, 1963; F. Hodler, U.S. Pat. No. 3,885,618, May 27, 1975; Hodler, U.S. Pat. No. 4,027,726, Jun. 7, 1977; Ernst et al., U.S. Pat. No. 4,729,422, Mar. 8, 1988; Runhlandt et al., U.S. Pat. No. 4,779,666, Oct. 25, 1988; Uchida et al., U.S. Pat. No. 4,782,886, Nov. 8, 1988; Voss et al., U.S. Pat. No. 4,809,767, Mar. 7, 1989; Voss et al., U.S. Pat. No. 4,825,933, May 2, 1989; Klenk, U.S. Pat. No. 4,832,109, May 23, 1989.
While the above patents appear to perform satisfactorily for their intended purpose, designers are always striving to improve the art.